eh it's fine. sure, technically speaking you're giving your machine over to whoever wrote that script. they could do anything! but actually, the script is usually useful and safe. Like this one.
You know that, I know that, but the thousands of people getting desensitized and trained to run random terminal commands like this to "fix their wi-fi" usually don't.
The problem isn't even pasting curl output into sh – it's instructing non-technical users to run any terminal commands, in my opinion.